1// -*- C++ -*-
  2//===----------------------------------------------------------------------===//
  3//
  4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  5// See https://llvm.org/LICENSE.txt for license information.
  6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  7//
  8//===----------------------------------------------------------------------===//
  9
 10#ifndef _LIBCPP___RANGES_DROP_WHILE_VIEW_H
 11#define _LIBCPP___RANGES_DROP_WHILE_VIEW_H
 12
 13#include <__algorithm/ranges_find_if_not.h>
 14#include <__assert>
 15#include <__concepts/constructible.h>
 16#include <__config>
 17#include <__functional/bind_back.h>
 18#include <__functional/reference_wrapper.h>
 19#include <__iterator/concepts.h>
 20#include <__ranges/access.h>
 21#include <__ranges/all.h>
 22#include <__ranges/concepts.h>
 23#include <__ranges/enable_borrowed_range.h>
 24#include <__ranges/movable_box.h>
 25#include <__ranges/non_propagating_cache.h>
 26#include <__ranges/range_adaptor.h>
 27#include <__ranges/view_interface.h>
 28#include <__type_traits/conditional.h>
 29#include <__type_traits/decay.h>
 30#include <__type_traits/is_nothrow_constructible.h>
 31#include <__type_traits/is_object.h>
 32#include <__utility/forward.h>
 33#include <__utility/in_place.h>
 34#include <__utility/move.h>
 35
 36#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 37#  pragma GCC system_header
 38#endif
 39
 40_LIBCPP_PUSH_MACROS
 41#include <__undef_macros>
 42
 43_LIBCPP_BEGIN_NAMESPACE_STD
 44
 45#if _LIBCPP_STD_VER >= 20
 46
 47namespace ranges {
 48
 49template <view _View, class _Pred>
 50  requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>>
 51class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS drop_while_view : public view_interface<drop_while_view<_View, _Pred>> {
 52public:
 53  _LIBCPP_HIDE_FROM_ABI drop_while_view()
 54    requires default_initializable<_View> && default_initializable<_Pred>
 55  = default;
 56
 57  _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 drop_while_view(_View __base, _Pred __pred)
 58      : __base_(std::move(__base)), __pred_(std::in_place, std::move(__pred)) {}
 59
 60  _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
 61    requires copy_constructible<_View>
 62  {
 63    return __base_;
 64  }
 65
 66  _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
 67
 68  _LIBCPP_HIDE_FROM_ABI constexpr const _Pred& pred() const { return *__pred_; }
 69
 70  _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
 71    // Note: this duplicates a check in `optional` but provides a better error message.
 72    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
 73        __pred_.__has_value(),
 74        "drop_while_view needs to have a non-empty predicate before calling begin() -- did a previous "
 75        "assignment to this drop_while_view fail?");
 76    if constexpr (_UseCache) {
 77      if (!__cached_begin_.__has_value()) {
 78        __cached_begin_.__emplace(ranges::find_if_not(__base_, std::cref(*__pred_)));
 79      }
 80      return *__cached_begin_;
 81    } else {
 82      return ranges::find_if_not(__base_, std::cref(*__pred_));
 83    }
 84  }
 85
 86  _LIBCPP_HIDE_FROM_ABI constexpr auto end() { return ranges::end(__base_); }
 87
 88private:
 89  _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
 90  _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Pred> __pred_;
 91
 92  static constexpr bool _UseCache = forward_range<_View>;
 93  using _Cache _LIBCPP_NODEBUG    = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
 94  _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
 95};
 96
 97template <class _View, class _Pred>
 98inline constexpr bool enable_borrowed_range<drop_while_view<_View, _Pred>> = enable_borrowed_range<_View>;
 99
100template <class _Range, class _Pred>
101drop_while_view(_Range&&, _Pred) -> drop_while_view<views::all_t<_Range>, _Pred>;
102
103namespace views {
104namespace __drop_while {
105
106struct __fn {
107  template <class _Range, class _Pred>
108  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pred&& __pred) const
109      noexcept(noexcept(/**/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))))
110          -> decltype(/*--*/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))) {
111    return /*-------------*/ drop_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred));
112  }
113
114  template <class _Pred>
115    requires constructible_from<decay_t<_Pred>, _Pred>
116  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pred&& __pred) const
117      noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>) {
118    return __pipeable(std::__bind_back(*this, std::forward<_Pred>(__pred)));
119  }
120};
121
122} // namespace __drop_while
123
124inline namespace __cpo {
125inline constexpr auto drop_while = __drop_while::__fn{};
126} // namespace __cpo
127} // namespace views
128} // namespace ranges
129
130#endif // _LIBCPP_STD_VER >= 20
131
132_LIBCPP_END_NAMESPACE_STD
133
134_LIBCPP_POP_MACROS
135
136#endif // _LIBCPP___RANGES_DROP_WHILE_VIEW_H